Motors, typically electric motors, are used to power pumps which inject chemicals into a process. A challenge with such motors is that the voltage delivered is not always consistent, causing the chemical output by the pump to vary. For example DC motors are commonly used to drive pumps. Some of these motors are powered by a solar power system and one or more batteries. When the batteries are low, for example due to days or nights in which no solar power is available, the voltage can drift down to, for example, about 12 volts. When the solar panel is charging the batteries when there is plentiful solar power, for example on sunny days, the voltage on the batteries can be higher, for example up to 13.5 volts. This difference in voltage, when applied to the DC motor driven pump system can result in a 10-15% difference in motor RPM, as the RPM of a DC motor is approximately proportional to the voltage applied. This in turn causes the delivery of inconsistent chemical rates to the process, which can vary by 10-15%. The result is a lower volume of injected chemical, for example at night, or a higher volume of injected chemical, for example during the sunny parts of days.